Color diffusion transfer photographic products,processes and compositions

ABSTRACT

Diffusion transfer process film units are disclosed which include a viscous processing composition including a filmforming, viscosity-providing polymer and colloidal silica. Substantially increased viscosity results from the inclusion of the colloidal silica. Color images, particularly multicolor integral negative-positive reflection prints, are obtained using the disclosed film units.

nit ed States Patent [1 1 l r [451 Dec. 4, 1973 [54] COLOR DIFFUSION TRANSFER 3,265,501 8/1966 Johnston 96/66 R PHOTOGRAPHIC PRODUCTS PROCESSES 3,266,894 8/1966 Weyerts et al 96/3 AND COMPOSITIONS Inventor: Edwin H. Land, Cambridge, Mass.

Assignee: Polaroid Corporation, Cambridge,

Mass.

Filed: Apr. 24, 1972 Appl. No.: 247,025

References Cited UNITED STATES PATENTS l2/l968 Land 96/29 D Primary Examiner-Norman G. Torchin Assistant ExaminerRichard l... Schilling Att0rney-Stanley H. Mervis et a1.

[57] ABSTRACT Diffusion transfer process film units are disclosed which include a viscous processing composition ineluding-a film-forming, viscosity-providing polymer and colloidal silica. Substantially increased viscosity results from the inclusion of the colloidal silica. Color images, particularly multicolor integral negativepositive reflection prints, are obtained using the disclosed film units.

50 Claims, No Drawings COLOR DIFFUSTON TRAlf J SFER PHOTOGRAPHIC PRODUQTS, PROCESSES ANlD COMPOSITIONS This invention is concerned with photography and,

more particularly, with diffusion transfer photographic products and processes employing a viscous processing composition.

Diffusion transfer processes performed in photographic apparatus of the self-developing type advantageously utilize a viscous processing composition to provide uniform distribution of reagents and dry processing, i.e., to aid in conforming the processing composition between two sheet-like elements and to aid in maintaining said elements in their requisite superposed relationship during the process. The desired viscosity may be provided by dissolving an alkali stable polymeric film-forming material in the processing composition. Particularly useful viscosity-providing, filmforming polymers comprise high molecular weight polymers such as polymeric, water-soluble cellulose ethers which are inert to an alkaline solution, e.g., a hydroxyethyl cellulose or sodium carboxymethyl cellulose as taught in U. S. Pat. No. 2,603,585 issued July 15, 1952 to Edwin H. Land. The film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 cps. at a temperature of approximately 24C. and preferably in the order of 100,000 to 200,000 cps. at that temperature. The processing composition may be releasably retained in a rupturable container until needed, as disclosed in said U. S. Pat. No. 2,603,565 and in other patents, including U. S. Pat. No. 2,543,l 81 issued Feb. 27, 1951 to Edwin H. Land.

The present invention has as its principal object the provision of a viscous processing composition useful in diffusion transfer processes comprising a film-forming polymer and an inorganic material which increases the viscosity provided by said polymer.

A further object of this invention is to provide viscous processing compositions which are particularly adapted for use in forming integral negative-positive reflection printed by diffusion transfer processing.

Yet another object of this invention is to provide diffusion transfer film units adapted for forming color transfer images, said film units including processing compositions containing a viscosity-providing polymer and a colloidally dispersed inorganic material, more particularly a colloidal silica.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features, properties and relation of components and the process involving the several steps and therelation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

As indicated above, this invention is concerned with diffusion transfer processes which utilize a viscous processing composition. In such processes, a thin substantially uniform layer of a processing composition is provided between two superposed sheet-like elements. In a typical process of this type, one of said sheet-like elements contains one or more photosensitive strata and the other sheet-like contains an image-receiving stratum for receiving an imagewise distribution of the image-forming components transferred by diffusion from the other or photosensitive element. In other processes, the image-receiving layer and the photosensitive layer(s) are initially present on a common support, and the second element functions as a spreader sheet to aid in distribution of the viscous processing composi tion and to confine it between said elements, the other surfaces of the superposed elements remaining dry. More recently, increased interest has occurred with respect to diffusion transfer processes wherein the developed photosensitive layer(s) and the transfer imagecontaining layer are maintained together as a permanent laminate; the resulting photographs may be referred to as integral negative-positive reflection prints. In such processes a light-reflecting layer is provided between the image-receiving layer and the photosensitive layer(s) so as to mask the developed photosensitive layers and to provide a background, preferably white, against which the transfer image may be viewed, A white pigment, preferably titanium dioxide,

is advantageously used to provide said light-reflecting layer and said white pigment may initially be present in the processing composition.

In the preferred embodiments of this invention, the transfer image is a dye image resulting from the use of dye developers in the development of an exposed silver halide emulsion; accordingly, the invention will be described for convenience by reference to its utilization in dye developer color transfer processes.

U. S. Pat. No. 2,983,606 issued May 9, 1961 to Howard G. Rogers, discloses the formation of diffusion transfer color images by the use of dye developers, i.e.,

a compound which is both a silver halide developing agent and a dye. A photosensitive element containing a dye developer and a silver halide emulsion is exposed and a viscous processing composition is distributed in a substantial uniform layer between the exposed photosensitive element and a superposed image-receiving layer. The processing composition is so applied and confined within and between the two sheet-like elements as not to contact or wet outer surfaces of the superposed elements, thus providing a film unit or film packet whose external surfaces are dry. The viscous processing composition preferably is distributed from a single-use rupturable container; such pressure rupturable processing containers are well known and are frequently referred to as pods. The liquid processing composition, distributed intermediate the photosensitive element and the image-receiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and

in part to a localized exhaustion of alkali as a result of development. In undeveloped and partially developed areas of the emulsion. the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer, diffusible in the liquid processing composition, as a function of the pointto-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element, said transfer substantially excluding oxidized dye developer. The image-receiving layer receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide a reversed or positive color image of the developed image. The imagereceiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. If the color of the transferred dye developer is affected by changes in the pH of the image-receiving element, this pH may be adjusted in accordance with I well-known techniques to provide a pH affording the desired color. In the preferred embodiments of said US. Pat. No. 2,983,606 and in current commercial applications thereof, the desired positive image is revealed by separating the image-receiving layer from the photosensitive element at the end of a suitable imbibition period. Alternatively, as also disclosed in said U. S. Pat. No. 2,983,606, the image-receiving layer need not be separated from the photosensitive element, subsequent to transfer image formation, if the support for the image-receiving layer, as well as any other layers intermediate said support and image-receiving layer, is transparent and a processing composition containing a substance, e.g., a white pigment, effective to mask the developed silver halide emulsion or emulsions is applied between the image-receiving layer and said silver halide emulsion or emulsions.

Dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function" is meant a grouping adapted to develop exposed silver halide. A preferred silver halide developing function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonid or quinone substances when oxidized.

Multicolor images may be obtained using dye developers in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned U. S. Pat. No. 2,983,606, and particularly with reference to FIG. 9 of the patents drawing, and also in U. S. Pat. No. 3,345,163 issued Oct. 3, 1967 to Edwin H. Land and Howard G. Rogers, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. Each set of silver halide emulsion and associated dye developer strata may be optionally separated from other sets by suitable interlayers, for example, by a layer or stratum of gelatin or polyvinyl alcohol. In certian instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be so employed and a separate yellow filter omitted.

The dye developers are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective silver halide emulsion applied by use of a coating solution containing the respective dye developer in a concentration calculated to give the desired coverage of dye developer per unit area, in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the diffusion transfer processing composition.

As examples of materials for use in the imagereceivng layer, mention may be made of partially hydrolyzed polyvinyl acetate; polyvinyl alcohol; gelatin; and other materials ofa similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U. S. Pat. No. 3,148,061, issued Sept. 8, 1964 to Howard C. Haas.

U. S. Pat. Nos. 3,415,644, 3,415,645 and 3,415,646, all issued December 10, l968 in the name of Edwin H. Land, disclose and claim photographic products and processes wherein a photosensitive element and an image-receiving element are maintained in fixed relationship prior to and during exposure, and this relationship is maintained as a laminate after processing and image formation to provide an integral negative-positive reflection print. In these processes, the final image is viewed through a transparent (support) element against a light-reflecting, i.e., white background. In a particularly useful embodiment, photoexposure is made through said transparent support and application of the processing composition provides a layer of lightreflecting material to provide a white background. The light-reflecting material (referred to in said patents and applications as an opacifying agent) is preferably titanium dioxide, and it also performs an opacifying operation, i.e., it is effective to mask the developed silver halide emulsions so that the transfer image may be viewed without interference therefrom, and it also helps to protect the photoexposed silver halide emulsions from post-exposure fogging by light passing through said transparent layer if the photoexposed film unit is removed from the camera before imageformation is completed.

U. S. Pat. No. 3,647,437 issued Mar. 7, 1972 to Edwin H. Land, is concerned with improvements in the above-mentioned processes, and discloses the provision of light-absorbing materials to permit such processes to be performed outside of the camera in which photoexposure is effected and under much more intense ambient light conditions. A light-absorbing material or reagent, preferably a dye, is provided so positioned and/or constituted as not to interfere with photoexposure but so positioned between the photoexposed silve halide emulsions and the transparent support during processing after photoexposure as to absorb light which otherwise might fog the photoexposed emulsions. The light-absorbing material is so positioned and/or constituted after processing as not to interfere with viewing the desired image shortly after said image has been formed. In the preferred embodiments, the light-absorbing material, also sometimes referred to as an optical filter agent, is initially contained in the processing composition together with a light-reflecting material, e.g., titanium dioxide. The concentration of the light-absorbing dye is selected to provide the light transmission opacity required to perform the particular process under the selected light conditions.

ln a particularly useful embodiment, the lightabsorbing dye is highly colored at the pH of the processing composition, e.g., l3-l4, but is substantially non-absorbing of visible light ata lower pH, e.g., less than l0-l2. This pH reduction may be effected by an acid-reacting reagent appropriately positioned in the film unit, e.g., in a layer between the transparent support and the image-receiving layer.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, sodium hydroxide, potassium hydroxide, and the like, and preferably processing a pH in excess of 12, and most preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, water-soluble ethers such as polymeric, water-soluble ethers which are inert to an alkaline solution such as, for exmaple, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Other film-forming polymers whose ability to increase viscosity is substantially unaffected if left in alkaline solution for a long period of time are also capable of utilization. As stated, the filmforming polymer is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 cps. at a temperature of approximately 24C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

As is known and recognized in the art, some filmforming, viscosity-providing polymers, particularly cellulose ethers such as carboxymethyl cellulose, are soluble in water only in the form of a salt thereof, e.g., an alkali metal or ammonium salt. The use of such watersoluble salts is to be understood as within the scope of the term water-soluble polymer as used herein.

It has now been found that the incorporation of colloidal silica in such viscous processing compositions provides a marked increase in viscosity and improved photographic properties, particularly when employed in diffusion transfer processes providing integral negative-positive reflection prints.

Colloidal silica as used herein is intended to refer to aqueous sols of widely dispersed discrete particles which are essentially amorphous silica (SiO 95% or more of the solid content of such sols is SiO The silica particles are extremely small, being on the order of millimicrons or smaller. The silica particles may have a smal quantity of sodium ions on the surface to prevent agglomeration. Particularly useful colloidal silicas are the sols of colloidal silica commercially available of E. l. du Pont de Nemours Co., Wilmington, Delaware, under the tradename Ludox colloidal silica. These sols contain about 30% by wieght silica and have viscosities of less than 15 cps. at 25C.

It has been found that the addition of colloidal silica to processing compositions containing water-soluble cellulose ethers, such as sodium carboxymethyl cellulose, (CMS) hydroxyethyl cellulose (HEC) and hydroxyethyl carboxymethyl cellulose sodium salt (HECMC), markedly increases the viscosity of the processing composition. Viscosity increases of as much as 2 to 5' times the viscosity provided by the cellulose ether alone may be readily obtained without reducing the utility of the processing composition in diffusion transfer processes. The resulting viscous processing compositions exhibit improved thiotropic properties, with increased resistance to flow when at rest and readily flowing when subjected to pressure.

When used in forming integral negative-positive reflection prints, the incorporation of colloidal silica in the processing composition may provide bond strength to the resulting laminate. When the applied layer of the processing composition solidifies by extraction of the water and drying, the mixture of colloidal silica and polymer appears to aid in preventing further transfer of reagents, including image dyes, to the image-receiving layer. The polymer-colloidal silica viscous processing compositions of this invention increase the dispersion stability of light-reflecting pigments, e.g., titanium dioxide, incorporated therein. Where the components of the integral negative-positive film unit used to provide an integral negative-positive film unit are temporarily laminated together prior to exposure, as by a layer of watersoluble polyethylene glycol, distribution of the processing composition being used to delaminate and then relaminate to form the final laminate, the polymer-colloidal silica viscous processing compositions provide a cleaner delamination with more uniform coverage, i.e., the polyethylene glycol layer is more uniformly separated. In addition, the marked increases in viscosity provided by the colloidal silica permits the use of less of the polymeric viscosity-providing agent.

The amount of colloidal silica to be added to the processing composition may be readily determined as a function of the viscosity and other properties desired for the particular diffusion transfer process. It has been found that useful processing compositions may be obtained by using a cellulose ether to colloidal silica (as SiO of from about 4 to l to about 1 to 2, a ratio of 2 to 1 being particularly useful. This ratio will vary in part as a result of the polymers own viscosity. The higher the colloidal silica content, the higher the viscosity will be.

The following example is given for purposes of illustration only:

EXAMPLE A photosensitive element was prepared by coating a gelatin-subsocated 4 mil opaque polyethylene teraphthalate film base with the following layers:

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about mgs./ft. of dye and about 8 0 mgs./ft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about mgs./ft. of silver and about 70 mgs./ft. of gelatin;

3. a layer of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, sytrene and methacrylic acid and polyacrylamide coated at a coverage of about 150 mgs./ft. of the copolymer and about mgs/ft. of polyacrylamide;

4. a layer of magenta dye developer dispersed in gelatin and coated at a coverage of about 1 l2 mgs./ft. of dye and about 100 mgs./ft. of gelatin;

5. a green-senstiive gelatino silver iodobromide emulsion coated at a coverage of about 100 mgs./ft. of silver and about 50 mgsjft. of gelatin;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 mgs./ft. of copolymer and about 12 mgs./ft. of polyacrylamide;

7. a layer of yellow dye developer dispersed in gelatin and coated at a coverage of about 70 mgs./ft. of dye and about 56 mgs./ft. of gelatin;

8. a blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4- methylphenyl hydroquinone coated at a coverage of about 120 mgs./ft. of silver, about 60 mgs./ft. of gelatin and about 30 mgs./ft. of auxiliary developer; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. of gelatin.

(The three dye developers employed were the ones recited above.)

A transparent 4 mil. polyethylene teraphthalate film base was coated, in succession, with the following layers to form an image-receiving component:

1. as a polymeric acid layer, the partially butyl ester of polyethylene/maleic anhydride copolymer at a coverage of about 2,500 mgs./ft.

2. a timing layer containing about a 40:1 ratio of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide at a coverage of about 500 mgs./ft. and

3. a polymeric image-recieving layer containing a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine, at a coverage of about 300 mgs./ft. The two components thus prepared were then taped together, in laminate form, at their respective edges to provide an integral film unit, with a rupturable container retaining an aqueous alkaline processing solution fixedly mounted on the leading edge of each of the components, by pressure-sensitive tapes, so that, upon application of compressive pressure to the container to rupture the container's marginal seal, its contents were distributed in a layer approximately 0.0026 inch thick between the image-receiving layer and the gelatin overcoat layer of the photosensitive component. The aqueous alkaline processing composition comprised:

Potassium hydroxide (85%) 5.3 g

N-benzyl-oz-picolinium bromide (50% solution in water) l.3 g. N-phenethyl-a-picolinium bromide 0.775g. Sodium carboxymethyl cellulose (Hercules Type 7H4F providing a viscosity of 3000 cps. at 1% in water at 25C.) 0.59 g.

Titanium dioxide 44.9 g.

6-methyl uracil 0.63 g.

bis-(B-aminoethyl)-sulfide 0.045g.

Lithium nitrate 0.1 g.

Benzotriazole 0.6 g.

6-methyl-5-bromo-4-azabenzimidazole 0.03 g.

Colloidal silica aqueous dispersion (30% SiO Lithium hydroxide 0.2 g. 6-benzylamino-purine 0.42 g. Polyethylene glycol (molecular weight 6000) 0.58

.S. Pat.

The photosensitive element was exposed through the transparent support and the layers thereon, the processing composition distributed by passing the film unit between a pair of pressure-applying rolls and into a lighted area. The laminate obtained by distribution of the processing composition was maintained intact to provide an integral negative-positive reflection print which exhibited good color quality and separation. In preparing the above processing composition, the polymer and the titanium dioxide were blended dry and then added to a solution containing all of the other reagents except the colloidal silica which was added last. The viscosity of the resulting viscous processing composition 24 hours after mixing was several times that of a control which did not include the colloidal silica.

The novel processing compositions of the present invention may be used in a variety of film structures adapted to provide integral negative-positive reflection prints, many of which are described in detail in the previously cited U. S. patents, e.g., U. S. Pat. Nos. 2,983,606; 3,415,644; 3,415,645; 3,415,646 and 3,647,437. Other useful integral negative-positive film units are described in U. S. Pat. Nos. 3,594,164 and 3,594,165 issued July 20, 1971 to Howard G. Rogers. For convenience, the disclosures of these patents are hereby incorporated by reference.

The image dye-providing materials which may be employed in such processes generally may be character- 1 ized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible or provide a diffusible product in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers. The requisite differential in mobility or solubility may, for example, be obtained by a chemical action such as a redox reaction or a coupling reaction.

As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U. Nos. 2,774,668; 2,968,554; 2,983,606; 2,087,817; 3,185,567; 3,230,082; 3,345,163; and 3,443,943. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U. S. Pat. Nos. 3,185,567; 3,443,939; 3,443,940; 3,227,550; and 3,227,552. Both types of image-dye providing substances and film units useful therewith also are discussed in the aforementioned U. S. Pat. No. 3,647,437 to which reference may be made.

In any of these systems, muticolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith an image dye-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripcak structures employing a blue-, a greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan image dye-providing material, as disclosed in U. S. Pat. No. 3,345,163 issued Oct. 3, 1967 to Edwin 11. Land and Howard G. Rogers. Alternatively, the silver halide emulsions may be present in the form of minute elements arranged in side-by side relationship in a photosensitive screen pattern as is well known and taught, for example, in the aforementioned U. 8. Pat. No. 2,983,606.

The image-receiving layer may comprise one of the materials known in the art, such as polyvinyl alcohol, gelatin, etc. It may contain agents adapted to mordant or otherwise fix the transferred image dye(s). Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U. S. Pat. No. 3,148,061, issued Sept. 8, 1964 to Howard G. Haas. 1f the color of the transferred .image dye(s) is affected by changes in pH, the pH of the image layer may be adjusted to provide a pH affording the desired color.

In the various color diffusion transfer systems which have previously been described and which employ an aqueous alkaline processing fluid, it is well known to employ an acid-reacting reagent in a layer of the film unit to lower the environmental pl-l following substantial dye transfer in order to increase the iamge stability and/or to adjust the pH from the first pH at which the image dyes are diffusible to a second (lower) pH at which they are not. For example, the previously mentioned U. S. Pat. No. 3,415,644 discloses systems wherein the desired pH reduction may be effected by providing a polymeric acid layer adjacent the dyeable stratum. These polymeric acids may be polymers which contain acid groups, e.g., carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals or with organic bases; or potentially acidyielding groups such as anhydrides or lactones. Preferably the acid polymer contains free carboxyl groups. Alternatively, the acid-reacting reagent may be in a layer adjacent the silver halide most distant from the imagereceiving layer, as disclosed in U. S. Pat. No. 3,573,043 issued Mar. 30, 1971 to Edwin H. Land. Another system for providing an acid-reacting reagent is disclosed in U. S. Pat. No. 3,576,625 issued Apr. 27, 1971 to Edwin H. Land.

An inert interlayer or spacer layer may be and is preferably disposed between the polymeric'acid layer and the dyeable stratum in order to control or time the pH reduction so that it is not premature or interfere with the development process. Suitable spacer or timer layers for this purpose are described with particularity in U. S. Pat. Nos. 3,362,819; 3,419,389; 3,421,893; 3,455,686; and 3,575,701.

While the acid layer and associated spacer layer are preferably contained in the positive component employed in systems wherein the dyeable stratum and photosensitive strata are contained on separate supports, e.g., between the support for the receiving element and the dyeable stratum; or associated with the dyeable stratum in those integral film units, e.g., on the side of the dyeable stratum opposed from the negative components, they may, if desired, be associated with the photosensitive strata, as is disclosed, for example, in U. S. Pat. Nos. 3,362,821 and 3, 573,043. In film units such as those described in the aforementioned U. S. Pat. Nos. 3,594,164 and 3,594,165,- they also may be contained on the spreader sheet employed to facilitate application of the processing fluid.

The incorporation of colloidal silica in a viscous processing composition in color transfer processes in accordance with this invention may be readily distinguished from the prior disclosure of U. S. Pat. No. 2,616,807 issuedNov. 4, l952 to E dwi nTl1at patent is directed to the formation of diffusion transfer images in a layer provided by the viscous processing composition and more specifically to imparting a matte finish to the resulting image. A plurality of finely comminuted substances are disclosed as suitable for providing a matte surface to a silver transfer image layer formed by solidification of a layer of processing composition, including such diverse substances as wood flour, silica aerogel, kieselguhr, etc. The silver transfer image is formed in the layer containing the finely comminuted substance or in a layer visible therethrough. In contrast, in the present invention the solidified layer of processing composition containing colloidal silica does not contain the transer image nor is the transfer image viewed therethrough. [n the preferred embodiments of this invention, the solidified layer of polymer and colloidal silica includes a white pigment, e.g., titanium dioxide, and provides a light-reflecting layer serving as a background against which a dye transfer image is viewed. In other embodiments of this invention, the processing composition layer containing colloidal silica may be physically separated from the image-receiving layer containing the desired color transfer image.

It will be understood that dye transfer images which are neutral or black-and-white instead of multicolor may be obtained by use of a mixture of dyes of the appropriate colors, the transfer of which may be controlled by a single layer of silver halide, in accordance with known techniques. It is also to be understood that direct positive silver halide emulsions may also be used, depending upon the particular dye imageproviding substances employed and whether a positive or negative color transfer image is desired.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A photographic product for forming a diffusion transfer image in dye within a permanent laminate including at least one developed silver halide layer, said photographic product comprising, in combination, an image-receiving layer; at least one silver halide emulsion, each said silver halide emulsion having associated therewith an image dye-providing substance selected from the group consisting of image dyes and image dye intermediates; means providing a light-reflecting layer between said image-receiving layer and said silver halide emulsion(s) to mask said silver halide emulsion(s) after development thereof and to provide a white background for viewing a dye image formed in said imagereceiving layer; a transparent support through which said dye image in said image-receiving layer may be viewed; said product including a rupturable container releasably retaining a viscous processing composition for developing said silver halide emulsion(s) after photoexposure and for forming a transfer image in at least one dye in said image-receiving layer; said rupturable container being positioned to distribute said processing composition between predetermined layers of said product; said viscous processing composition including a film-forming, viscosity-providing polymer and colloidal silica.

2. A photographic film as defined in claim 1 wherein each said image dye-providing substance is a dye.

3. A photographic film as defined in claim 2 wherein each said dye is a dye developer.

4. A photographic film .as defined in claim 1 wherein each said image dye-providing substance is an intermediate for an image dye.

5. A photographic product as defined in claim 1 wherein said silver halide emulsion(s) are adpated to be exposed through said transparent support.

6. A photographic product as defined in claim 1 wherein said means providing a light-reflecting layer comprise a white pigment dispersed in said processing composition, and said rupturable container is positioned to distribute said processing composition containing said pigment between said image-receiving layer and said silver halide emulsion(s).

7. A photographic product as defined in claim 1 comprising a temporary laminate including said layers confined between two dimensionally stable supports, at least one of said supports being transparent, the bond between a predetermined pair of layers being weaker than the bond between other pairs of layers, said rupturable container being so positioned as to distribute said processing composition between said predetermined layers, said processing composition being adapted to provide said permanent laminate following distribution and drying.

8. A photographic product as defined in claim 1 wherein said transparent support is a polyester.

9. A photographic product as defined in claim 8 wherein said polyester is polyethylene terephthalate.

10. A photographic product as defined in claim 1 wherein said transparent support is cellulose acetate.

11. A photographic product as defined in claim 1 wherein said polymer is a water-soluble cellulose ether.

12. A photographic product as defined in claim 11 wherein said cellulose ether is a hydroxyethyl cellulose.

13. A photographic product as defined in claim 11 wherein said cellulose ether is an alkali metal salt of a carboxymethyl cellulose.

14. A photographic product as defined in claim 11 wherein said cellulose ether is a hydroxyethyl carboxymethyl cellulose.

15. A photographic product as defined in claim 1, wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to l to about 1 to 2. 7

16. A photographic product as defined in claim 1 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to l.

17. A photographic product as defined in claim 16 said polymer is sodium carboxymethyl cellulose.

18. A photographic product comprising a first support; a red-sensitive silver halide emulsion; a greensensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer; an image-receiving layer for receiving image dyes transferred thereto by diffusion as a function of exposure and development of said silver halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed; a rupturable container releasably holding a processing composition adapted, upon distribution between predetermined layers of said film to develop said silver halide emulsions and to effect the formation of a transfer image in dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developed silver halide emulsions and said image-receiving layer; and means providing a light-reflecting layer between said image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed silver halide emulsions; said processing composition including a film-forming, viscosity-providing polymer and colloidal silica.

19. A photographic product as defined in claim 18 wherein said polymer is a water-soluble cellulose ether.

20. A photographic product as defined in claim 19 wherein said cellulose ether is an alkali metal salt of a carboxymethyl cellulose.

21. A photographic product as defined in claim 18 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to l to about I to 2.

22. A photographic product as defined in claim 18 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to l.

23. A photograhic product as defined in claim 18 wherein the individual silica particles are about millimicrons in size.

24. A photographic product as defined in claim 18 wherein said means for providing a light-reflecting layer comprises a white pigment dispersed in said processing composition.

25. A photographic product as defined in claim 18 wherein said first support is opaque.

26. A photographic product as defined in claim 18 wherein said transparent support is a polyester.

27. A photographic product as defined in claim 26 wherein said polyester is polyethylene teraphthalate.

28. A photographic product as defined in claim 25 wherein said opaque support is polyethylene teraphthalate.

29.-A photographic product as defined in claim 18 wherein said transparent support is cellulose acetate.

30. A photographic product as defined in claim 18 wherein said transparent support and said imagereceiving layer comprise a separate element adapted to be brought into superposed relationship with said silver halide emulsions.

31. A photographic product as defined in claim 18 wherein said layers are held in fixed relationship between said supports prior to and during exposure.

32. A photographic product as defined in claim 31 wherein said fixed relationship is provided by binder means along at least two parallel sides of said product.

33. A photographic product as defined in claim 31 wherein said product is a laminate of said layers between said first and said second supports, the bond between a predetermined pair of layers being weaker than the bonds between the other layers, said rupturable container being so positioned as to release said processing composition for distribution between said predetermined pair of layers.

34. A photographic product as defined in claim 18 wherein said silver halide emulsions are present as separate planar layers.

35. A photographic product as defined in claim 18 wherein said silver halide emulsions are present in the form of minute elements arranged in side-by-side relationship in a photosensitive screen pattern.

36. A photographic product as defined in claim 34 38. A photographic product as defined in claim 18 including means to reduce the pH of a layer of said processing composition from a first pH to a second pH.

39. A photographic product as defined in claim 38 wherein said means to reduce the pH comprises a layer of an acid-reacting reagent positioned between said transparent support and said image-receiving layer.

40. A photographic product as defined in claim 39 wherein said acid-reacting reagent is a polymer.

41. A photographic product as defined in claim 18 wherein said processing composition includes an optical filter agent which is colored at the pH of said processing composition, said optical filter agent being adapted to be rendered colorless by reducing said pH.

42. In a method of forming a diffusion transfer dye image by providing an exposed silver halide emulsion, forming an imagewise distribution of a diffusible dye image-providing substance as a function of said development, and transferring at least a portion of said imagewise distribution of diffusible dye image-providing substance to an image-receiving layer in superposed relationship with said silver halide emulsion to provide said dye image, said image-receiving layer and said silver halide emulsion forming a permanent laminate including a light-reflecting layer positioned between said image-receiving layer and said silver halide emulsion, the step of applying the processing composition in a thin layer between said exposed silver halide emulsion and another layer, said processing composition comprising a fluid rendered thixotropic by the inclusion therein of a water-soluble, film-forming polymer and colloidal silica.

43. The method as defined in claim 42 wherein said diffusible dye image-providing substance is a dye developer.

44. The method as defined in claim 42 wherein a redsensitive silver halide emulsion, a green-sensitive silver halide emulsion and a blue-sensitive silver halide emulsion are present, said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, and said dye image is a multicolor image.

45. The method as defined in claim 42 wherein said processing composition includes a light-reflecting agent.

46. The method as defined in claim 45 wherein said light-reflecting agent is a white pigment.

47. The method as defined in claim 46 wherein said white pigment is titanium dioxide.

48. The method as defined in claim 42 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to l to about 1 to 2.

49. The method as defined in claim 42 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to l.

50. The method as defined in claim 42 wherein the individual silica particles are about 15 millimicrons in size. 

2. A photographic film as defined in claim 1 wherein each said image dye-providing substance is a dye.
 3. A photographic film as defined in claim 2 wherein each said dye is a dye developer.
 4. A photographic film as defined in claim 1 wherein each said image dye-providing substance is an intermediate for an image dye.
 5. A photographic product as defined in claim 1 wherein said silver halide emulsion(s) are adpated to be exposed through said transparent support.
 6. A photographic product as defined in claim 1 wherein said means providing a light-reflecting layer comprise a white pigment dispersed in said processing composition, and said rupturable container is positioned to distribute said processing composition containing said pigment between said image-receiving layer and said silver halide emulsion(s).
 7. A photographic product as defined in claim 1 comprising a temporary laminate including said layers confined between two dimensionally stable supports, at least one of said supports being transparent, the bond between a predetermined pair of layers being weaker than the bond between other pairs of layers, said rupturable container being so positioned as to distribute said processing composition between said predetermined layers, said processing composition being adapted to provide said permanent laminate following distribution and drying.
 8. A photographic product as defined in claim 1 wherein said transparent support is a polyester.
 9. A photographic product as defined in claim 8 wherein said polyester is polyethylene terephthalate.
 10. A photographic product as defined in claim 1 wherein said transparent support is cellulose acetate.
 11. A photographic product as defined in claim 1 wherein said polymer is a water-soluble cellulose ether.
 12. A photographic product as defined in claim 11 wherein said cellulose ether is a hydroxyethyl cellulose.
 13. A photographic product as defined in claim 11 wherein said cellulose ether is an alkali metal salt of a carboxymethyl cellulose.
 14. A photographic product as defined in claim 11 wherein said cellulose ether is a hydroxyethyl carboxymethyl cellulose.
 15. A photographic product as defined in claim 1, wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to 1 to about 1 to
 2. 16. A photographic product as defined in claim 1 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to
 1. 17. A photographic product as defined in claim 16 said polymer is sodium carboxymethyl cellulose.
 18. A photographic product comprising a first support; a red-sensitive silver halide emulsion; a green-sensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer; an image-receiving layer for receiving image dyEs transferred thereto by diffusion as a function of exposure and development of said silver halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed; a rupturable container releasably holding a processing composition adapted, upon distribution between predetermined layers of said film to develop said silver halide emulsions and to effect the formation of a transfer image in dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developed silver halide emulsions and said image-receiving layer; and means providing a light-reflecting layer between said image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed silver halide emulsions; said processing composition including a film-forming, viscosity-providing polymer and colloidal silica.
 19. A photographic product as defined in claim 18 wherein said polymer is a water-soluble cellulose ether.
 20. A photographic product as defined in claim 19 wherein said cellulose ether is an alkali metal salt of a carboxymethyl cellulose.
 21. A photographic product as defined in claim 18 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to 1 to about 1 to
 2. 22. A photographic product as defined in claim 18 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to
 1. 23. A photograhic product as defined in claim 18 wherein the individual silica particles are about 15 millimicrons in size.
 24. A photographic product as defined in claim 18 wherein said means for providing a light-reflecting layer comprises a white pigment dispersed in said processing composition.
 25. A photographic product as defined in claim 18 wherein said first support is opaque.
 26. A photographic product as defined in claim 18 wherein said transparent support is a polyester.
 27. A photographic product as defined in claim 26 wherein said polyester is polyethylene teraphthalate.
 28. A photographic product as defined in claim 25 wherein said opaque support is polyethylene teraphthalate.
 29. A photographic product as defined in claim 18 wherein said transparent support is cellulose acetate.
 30. A photographic product as defined in claim 18 wherein said transparent support and said image-receiving layer comprise a separate element adapted to be brought into superposed relationship with said silver halide emulsions.
 31. A photographic product as defined in claim 18 wherein said layers are held in fixed relationship between said supports prior to and during exposure.
 32. A photographic product as defined in claim 31 wherein said fixed relationship is provided by binder means along at least two parallel sides of said product.
 33. A photographic product as defined in claim 31 wherein said product is a laminate of said layers between said first and said second supports, the bond between a predetermined pair of layers being weaker than the bonds between the other layers, said rupturable container being so positioned as to release said processing composition for distribution between said predetermined pair of layers.
 34. A photographic product as defined in claim 18 wherein said silver halide emulsions are present as separate planar layers.
 35. A photographic product as defined in claim 18 wherein said silver halide emulsions are present in the form of minute elements arranged in side-by-side relationship in a photosensitive screen pattern.
 36. A photographic product as defined in claim 34 wherein said blue-sensitive silver halide emulsion layer is between said image-receiving layer and said other silver halide emulsion layers.
 37. A photographic product as defined in claim 34 wherein said blue-sensitive silver halide emulsion layer is between saiD first support and said other silver halide emulsion layers, and said first support is transparent.
 38. A photographic product as defined in claim 18 including means to reduce the pH of a layer of said processing composition from a first pH to a second pH.
 39. A photographic product as defined in claim 38 wherein said means to reduce the pH comprises a layer of an acid-reacting reagent positioned between said transparent support and said image-receiving layer.
 40. A photographic product as defined in claim 39 wherein said acid-reacting reagent is a polymer.
 41. A photographic product as defined in claim 18 wherein said processing composition includes an optical filter agent which is colored at the pH of said processing composition, said optical filter agent being adapted to be rendered colorless by reducing said pH.
 42. In a method of forming a diffusion transfer dye image by providing an exposed silver halide emulsion, forming an imagewise distribution of a diffusible dye image-providing substance as a function of said development, and transferring at least a portion of said imagewise distribution of diffusible dye image-providing substance to an image-receiving layer in superposed relationship with said silver halide emulsion to provide said dye image, said image-receiving layer and said silver halide emulsion forming a permanent laminate including a light-reflecting layer positioned between said image-receiving layer and said silver halide emulsion, the step of applying the processing composition in a thin layer between said exposed silver halide emulsion and another layer, said processing composition comprising a fluid rendered thixotropic by the inclusion therein of a water-soluble, film-forming polymer and colloidal silica.
 43. The method as defined in claim 42 wherein said diffusible dye image-providing substance is a dye developer.
 44. The method as defined in claim 42 wherein a red-sensitive silver halide emulsion, a green-sensitive silver halide emulsion and a blue-sensitive silver halide emulsion are present, said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer, and said dye image is a multicolor image.
 45. The method as defined in claim 42 wherein said processing composition includes a light-reflecting agent.
 46. The method as defined in claim 45 wherein said light-reflecting agent is a white pigment.
 47. The method as defined in claim 46 wherein said white pigment is titanium dioxide.
 48. The method as defined in claim 42 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of from about 4 to 1 to about 1 to
 2. 49. The method as defined in claim 42 wherein said polymer and said colloidal silica are present in said processing composition in a ratio of about 2 to
 1. 50. The method as defined in claim 42 wherein the individual silica particles are about 15 millimicrons in size. 